Traditional window-type room air conditioners typically include a very basic thermostatic control mechanism which suffers from a number of disadvantages. One such disadvantage is that while the refrigerant compressor starts and stops to regulate the temperature of the room, the unit's fan does not. Thus, when the room is too warm the fan will continue to run even if the desired room temperature has been met. This thermostatic control method is inefficient from an energy usage standpoint, causes needless noise, and may result in overcooling of the room if, for example, it becomes cooler outdoors than the desired indoor temperature.
Another disadvantage of traditional thermostatic control mechanisms is that the temperature sensor is typically located in the air intake. This is where the temperature of the room is sampled, and where it is determined whether further cooling is necessary to achieve the desired temperature. If it gets cool outside during the night, for example, the air conditioner will continue to run in fan only mode, the compressor off, in an attempt to moderate the rooms temperature. The body of the unit will become cool and in effect it will cause the room to get cooler than is desired.
While some traditional window-type air conditioners do include some sort of advanced thermostatic controls which do stop and start the fan as an option, it is only the newest and most expensive units which do so. Moreover, even these units monitor the room's temperature through the intake air vent. However, this is also flawed since this thermostat is designed to measure the temperature of air passing by it. When the fan is off the unit is slow to respond to temperature demand and as a result does not work well.
Various attempts have been made to obviate the above problems, each attempt having met with varying degrees of success. U.S. Pat. No. 3,486,081, for example, discloses a thermostatic switch and adapter assembly for controlling the operation of an electrical heater or air conditioner unit as a function of temperature in a region remote from the unit. The assembly comprises an adapter box and a remote thermostatic switch connected to the box via a relatively light, two-wire extension line which may be of any desired length. The thermostatic switch is mounted at any desired position in the room and can be of the usual bimetallic design. The thermostat also includes a regulator knob to adjust the position of a fixed contact with respect to the moveable element, thereby to fix the temperature setting at which the switch closes.
U.S. Pat. No. 3,785,165 similarly discloses a thermostatic air conditioner control for use with individual unit air conditioners having a thermostatic switch disposed at a location remote from the air conditioner. The control includes circuitry interposed between the air conditioner and a source of electrical energy operative a selected time interval after closure of said thermostatic switch to energize a socket in which the air conditioner is plugged, and operative a selected time interval after opening of said thermostatic switch to de-energize the socket.
While U.S. Pat. Nos. 3,486,081 and 3,785,165 did obviate many of the above-described problems associated with the prior art, numerous problems with the prior art were not addressed thereby.
One such problem concerns the lack of an automatic “set-back” function. For ideal comfort or for energy conservation reasons, it is common practice to reduce the degree of cooling or heating during periods of minimum activity, for example during nighttime or at other times of minimum activity, according to comfort requirements. For example, the ambient temperature in a home can be reduced significantly at night when the occupants are asleep without causing any discomfort. Additionally, the temperature can be reduced substantially during the day when the dwelling is not occupied. Such a reduction in the nighttime temperature of the dwelling is referred to as a “set-back” which results in a significant reduction in fuel consumption and heating or cooling costs for the dwelling. With the conventional thermostats described above, such temperature set-backs are required to be carried out manually. The need to manually alter the regulated temperature is subject to the human failure of forgetting to change the thermostatic setting whereby cost savings are lost. Also, manual alteration of the regulated temperature is not entirely satisfactory since the dwelling will be uncomfortably cool in the morning before it is manually reset and, due to the lag time of typical heating systems, time is required for the temperature of the dwelling to rise to a comfortable level for normal daytime activities.
While automatic set-back has been provided by thermostats used in conjunction with higher-scale, feature-rich HVAC systems, such features have never been incorporated in the retro-fit type thermostatic control device which can be used with traditional window-type room air conditioners with which the present application is concerned.
Another problem with the systems disclosed in the above-referenced patents relates the lack of important safety features that inhibit potential fire and use of the device on an air conditioner of a size too large for the intended use. There is nothing preventing a user from plugging an air conditioner twice the size of the units' rating into the thermostatic control device. The prior art devices rely upon the wall outlet's circuit breaker which is in the main breaker box of the house to prevent overload. This breaker could require two or three more times the power to cause it to go on safety and as a result the prior art devices would receive more current than they are designed to receive and subsequently fail. Another condition that can happen is that the air conditioner itself could fail and cause a short circuit. The short may not be enough to cause the main circuit breaker to fail, but just enough to overpower the device and cause a catastrophic failure (i.e., a fire).
What is desired therefore, is an air conditioner control assembly for use with a room air conditioner which can be used with inexpensive units and/or with units already owned by the user, which accurately controls the temperature within the room, which is efficient from an energy usage standpoint and does not cause needless noise, and which does not rely on an air sample taken at the unit's air inlet, which allows for automatic set-back control to provide improved comfort control and energy conservation, and which incorporates safety features that inhibit potential fire and overload of the control assembly.